Fluid-cooled current converter



Nov. 23, 1948. H. MEES- FLUID-COOLED CURRENT CONVERTER Filed July 9, 1946 HERMAN MEES Patented Nov. 23, 1948 FLUID-COOLED CURRENT CONVERTER Herman Mees, Lodelinsart, Belgium, assignor to Ateliers de Constructions Electriques de Charleroi, Brussels, Belgium Application July 9, 1946, Serial No. 682,259 In France July 11, 1945 It is known that, in mercury vapor current converters of the liquid cathode type, a mercury vapor current is established which flows from the cathode towards the various parts of the converter, being condensed on the coolest parts of the latter before returning to the cathode in the form of liquid mercury.

This rising vapor current creates on the inside of the converter a certain mercury vapor pressure, the magnitude of which may substantially influence the proper operation of the converter.

More particularly, a zone of high mercury vapor pressure may be created around the cathode, which pressure may, under certain conditions, result in the elimination of the valve effect of the converter. This phenomenon, which may be regarded as normal, is greatly accentuated when the converter handles charges approaching its maximum charge capacity or when excess charges are applied to it.

This high mercury vapor pressure is a function of the cooling intensity of the walls of the converter and also of the distance which separates these cooled walls from the zone immediately about-thecathode. In metallic tank converters of high power and therefore of large dimensions, the distance between these two elements, the cooling wall on the one hand and the high pressure zone on the other hand, is such that, regardless of the cooling power of the cold wall, it is not possible by acting solely on this wall to reduce the pressure of the mercury vapor in the immediate vicinity of the cathode.

Under these conditions, the rectifying arc is developed in a zone of high mercury vapor pressure, in a region where normally the creation of .a good vacuum and therefore of a low vapor pressure is necessary for proper functioning of the converter. 1 i

It has therefore been necessary to intensify the cooling, particularly to bring cooling elements into the proximity of the high mercury vapor pressure zone, which elements are capable of condensing a part. of this vapor and consequently of reducing the density thereof, thus obviating the risk of eliminating the valve effect of the converter.

Various cooling circuit arrangements have been proposed for this purpose, several of whichto water-cooled current con- 9 Claims. (01. 250-275) anode crown, and the walls of which are cooled. The cooling action of this dome can be enhanced by adding to the lower part thereofa central cooling device traversed by cooling fluid and depending into the high pressure mercury vapor zone. In certain cases where the removal of heat by this cooling device is sufficient, the dome may be dispensed with since the bulk of the heat released is removed by the cooling device.

The central cooling device may, more particularly, be constituted by one or several tubes of large diameter, into which extend other tubes of smaller diameter. This cooling assembly then extends down to the high mercury vapor pressure :cathodic zone, the cooling fluid circulating for example first through the large tubes and then through the smaller tubes, by the action of cen tral suction.

It is possible to provide tubes of circular or flattened cross-section extending across the vat or tank of the converter from the bottom of the cathode-carrying sleeve Or collar to the anodecarrying lid. These tubes, traversed by the cooling fluid, are'located on the interior of the anode crown and consequently at the periphery of the cathodic mercury vapor high pressure zone.

According to constructional facilities and depending upon the intensity of the cooling, these tubesmay be straight or curved-in so as to present a rounded surface penetrating into the high vapor pressure zone, the latter arrangement improving the efiicacy of the cooling. In some cases, it is possible to so configure the bundle of tubes that they envelop the high pressure vapor zone, thus enhancin the intensity of the cooling.

All these known devices have been used in principle for cooling water-cooled metal tank current converters. The complications of watercooled installations, however, have led to attempts to operate mercury vapor converters with a cooling fluid such as air, which does not require complicated supply and discharge arrangements. However, in view of the great reduction in the coefficient of convection of iron-air with respect to iron-water, it was necessary to increase the cooling surfaces, so that the problem of the high powers has also appeared for the air-cooled mercury vapor converters.

Certain arrangements which could be used for water-cooling could not be adapted to air-cooled current converters. Thus, the spiral cooler utilizable with water can not be used for air, because the heat removal entails very high speeds within the tubes and, consequently, serious charge losses. It was, however, possible to adopt other arrangements. These are, in particular, the converter with cooling or condensing dome, with tubes traversed by the cooling fluid, i. e. air, and extending across the tank from the cathodecarrying sleeve or collar to the anode-carrying lid. A central cooling device has even been made up of a tubeof large diameter; onsthe: inside of.

which is=a tube of'smaller diameter, the air being sucked through this central tube.

Each of these arrangements involves certain: drawbacks.

The disposition of the metallic tank of a mercury vapor converter with a condensation dome, while being simple in construction; does not permit of direct access to the high mercury vapor pressure zone. The action of the dome is therefore a remote action, and even though the distance be small, it is still sufficient to let subsist, under certain conditions of operation, aregionof excess vapor pressure capable of starting a backfire: and thus of entailing the elimination of the valveeffect of the converter.

An' equally simple constructional arrangement is that with a central cylindrical or conical: coolingtdevice depending intothe high. vapor: pressure cathodic region, but it allows of a limited condensation of the vapor as a result of the double limitation in the surface in contact with; the vapor, on theonehand, andthe cooling 'airvelocity',.onithe: other hand;

Finally, while the embodiment with. multiple tubes traversing the converter tankirom cathode c'arryin'g sleeve: or collar to anode-carrying lid permits the direct cooling of the. high vapor pressure zone, it presents difficulties in actual. practice, particularly as regards joints. for the anode-carrying lid.

None of these embodiments therefore provides? a solution of the problem of cooling, by means of air, the high power mercury vapor current converter with a metallic tank.

The present invention relates to a new cooling device for this type of current converter, and is particularly adapted to prevent the formation of a high mercury vapor cathode region capable of eliminating the valve effect of the converter.

To this end, there is arranged within the metallic' tank of the converter a cooling device, morepa'rticularly a bundle of tubes, freelysuspend'ed from the anode-carrying lid of the converter and traversed by a cooling fluid, for example air. The

device is characterized by the fact that the inlet and outlet of the cooling fluid are disposed in ad} jacent parts of the anode-carrying lid of the converter, said parts being separated by a partition functioning as a flue, for instance an air shaft. It is further characterized by the fact that all the tubular cooling circuits extending across the inside of the tank are traversed in parallel by thecooling fluid, the latter being put into motion by a single source of energy, for instance asuction fan. 1

On the accompanying sheet of drawing:

Fig. l is a diagrammatic representation, in cross-section, of a presently-preferred exemplary embodiment of a high power mercury vapor current converter according to the invention; and

Fig, 2 is a diagrammatic representation of a modified detail.

For the sake of clarity, every detail not indispensable for an understanding of the invention has been omitted;

The metallic tank C of the converter is provided at its upperzend with: an anode-carrying lid P- the anodes being shown at A-and at its lower end with a cathode K. A jacket G encompasses the tank C, as shown, and the intermediate space, coextensive with the peripheral extent of the wall of the tank and with its conical bottom, may house cooling means in the form of conduits of any suitable cross section. Alternatively, and as shown, cooling. baffles m. may be.- provided' extendi'ng over the entire peripheral surface of tank 0 and over its conical bottom. A cooling fluid such as air may be blown through the aforesaid intermediate space, use being made for this purpose of any suitable circulating device such as a blower, fan, pump or the like (not shown). The stream of cooling fluid, flowing by in contact with baflles m, withdraws heat transmitted therethrough.

The cathode region is delineated in broken lines and; is designated by reference character R. As hereinbefore explained, the vapor pressure or density-in the cathode region R will be a function of the temperature of the side wall of tank 0, on the one hand, and of the distance D Whicnseparates this wall from. the region R, on the other hand; As the size of the converter increaseS aQ magnitude is reached wherein the distance. D becomes so great that the side wall of the tankhas practically no influence on thezregion R: withhigh. mercury vapor pressure, whatever the. tempera ture may be.

In order to reduce the distance D-from thehigha mercury vapor pressure region R. by cooling, a bundle-of tubes T is, according to the invention, freely suspended" from the anode-carryingv lid P and extends down into the region of high-pressure. R. The tubes of this bundle are traversed for instance. by air, put into motion by the. electtrically-actuated fan V, from the inlets e. to theoutlets s of the tubes, which are thus traversed in. parallel. The. inlets e and the outlets s are separated by an. air: shaft 9* which also: provides-the supporting means for the fan-carrying spiders h... In this way, the cooling action is brought directly to the inside of the high pressure zone R th-e distance D separating the latter from. the. coolin v meansbecoming zero.

The number of tubes comprising the tube bun. dles' may, of course, be varied, the numberbeing: shown on the drawing being merely illustrative. The downward extent of the several tubes, the configuration of which as shown: is preferably- U-shap'ed in character, is such that the regionR is penetrated thereby. The U-configuration may be varied, however, and the tubes may for example be incurved toward the high pressure mercury vapor pressure region R, as shown for example in the detail of Fig. 2, so as to increase the influence of the cooling on the latter.

The cooling tubes T may, if desired, be arranged in series with the cooling device m, whereby a. common source of power-fan, blower or the likemay be used for circulating fluid through both coolin arrangements. The circulation is established so that the cooling fluid circulates from the top of the tank toward the cathode.

The diameter of the tubes T is not critical.

and may be varied within considerable. limits;

The tubes are preferably made of metal.

The cooling device for the high pressure. mercury vapor'cathodic zone, realized by the presentv invention, therefore presents, with relation to prior arrangements, the double advantage. of a. complete cooling efficacy for the high pressure zone, combined with a simplicity of construction perfectly adaptable to the metallic tanks of converters of current construction.

Having thus disclosed the invention, what is claimed is:

1. In a high-power mercury vapor current converter, a metallic tank, a cathode at the bottom of said tank, whereby a zone of high mercury vapor pressure tends to be established above said cathode, an anode-carrying lid on said tank having the anodes arranged circularly thereon air cooling means freely suspended from said lid located within said anodes and extending downwardly into the said zone whereby the tendency to build up high pressure in said zone is minimized.

2. In a high-power mercury vapor current converter, a metallic tank, a cathode at the bottom of said tank, whereby a zone of high mercury vapor pressure tends to be established above said cathode, an anode-carrying lid on said tank, a tubular bundle freely suspended from said lid within the anodes on said lid and extending downwardly into the said zone, and means for circulating cooling fluid through said bundle, whereby the tendency to build up high pressure in said zone is minimized.

3. In a high-power mercury vapor current converter, a metallic tank, a cathode at the bottom of said tank, whereby a zone of high mercury vapor pressure tends to be established above said cathode, an anode-carrying lid on said tank, a tubular bundle freely suspended from said lid within the anodes on said lid and extending downwardly into the said zone, and means for circulating cooling fluid through said bundle, whereby the tendency to build up high pressure in said zone is minimized, the inlets to and outlets from said tubular bundle bein disposed in adjacent portions of said lid.

4. In a high-power mercury vapor current converter, a metallic tank, a cathode at the bottom of said tank, whereby a zone of high mercury vapor pressure tends to be established above said cathode, an anode-carrying lid on said tank, a tubular bundle freely suspended from said lid Within the anodes on said lid and extending downwardly into the said zone, and means for circulating cooling fluid through said bundle, whereby the tendency to build up high pressure in said zone is minimized, the inlets to and outlets from said tubular bundle being disposed in adjacent portions of said lid, and a partition defining an air shaft separating said lid portions.

5. In a high-power mercury vapor current converter, a metallic tank, a cathode at the bottom of said tank, whereby a zone of high mercury vapor pressure tends to be established above said cathode, an anode-carrying lid on said tank, a tubular bundle freely suspended from said lid within the anodes on said lid and extending downwardly into the said zone, and means for circulating cooling fluid through said bundle, whereby the tendency to build up high pressure in said zone is minimized, said tubular bundle comprising a plurality of substantially U-shaped conduits whereby a plurality of streams of cooling fluid traverse said conduits in parallel.

6. In a high-power mercury vapor current converter, a metallic tank, a cathode at the bottom of said tank, whereby a zone of high mercury 6 vapor pressure tends to be established above said cathode, an anode-carrying lid on said tank, a tubular bundle freely suspended from said lid within the anodes on said lid and extending downwardly into the said zone, and means for circulatin cooling fluid through said bundle, whereby the tendency to build up high pressure in said zone is minimized, said tubular bundle comprising a plurality of substantially U-shaped conduits whereby a plurality of streams of cooling fluid traverse said conduits in parallel, the inlet to and outlet from each U-shaped conduit being severally disposed in adjacent portions of said lid, and a partition separating said portions.

7. In a highepower mercury vapor current converter, a metallic tank, a cathode at the bottom of said tank, whereby a zone of high mercury vaporpressure tends to be established above said cathode, an anode-carrying lid on said tank, a tubular bundle freely suspended from said lid within the anodes on said lid and extending downwardly into the said zone, and means for circulating cooling fluid through said bundle, whereby the tendency to build up high pressure in said zone is minimized, said tubular bundle comprising a plurality of substantially U-shaped conduits, each conduit having a portion curved into the said zone.

8. In a high-power mercury vapor current converter, a metallic tank, a cathode at the bottom of said tank, whereby a zone of high mercury vapor pressure tends to be established above said cathode, an anode-carrying lid on said tank, cooling means freely suspended from said lid within the anodes on said lid and extending downwardly into the said zone whereby the tendency to build up high pressure in said zone is minimized, a cooling jacket about said tank, and means for producing a stream of cooling fluid through said coolin means and through said cooling jacket.

9. In a high-power mercury vapor current converter, a metallic tank, a cathode at the bottom of said tank, whereby a zone of high mercury vapor pressure tends to be established above said cathode, an anode-carrying lid on said tank, a tubular bundle freely suspended from said lid within the anodes on said lid and extending downwardly into the said zone, and means for circulatin cooling fluid through said bundle, whereby the tendency to build up high pressure in said zone is minimized, the inlets to and outlets from said tubular bundle being disposed in adjacent portions of said lid, and a partition defining an air shaft separating said lid portions, said circulating means being disposed in said air shaft.

HERMAN MEES.

REFERENCES CITED The following references are of record in the file of this patent:

FOREIGN PATENTS Number Country Date 206,303 Switzerland Nov. 16, 1937 206,306 Switzerland Nov. 1, 1939 464,741 Great Britain Apr. 23, 1937 

